Audiometric tests designed to detect malformations of the inner ear generally involve the measurement of the acoustic impedance at various frequencies in the audible range. Aside from their clinical uses, such measurements are also important in the technical field to facilitate the construction of simulated impedances utilized in checking the performance of intra-aural devices such as hearing aids, stethoscopic headphones and earplugs.
The conventional method of measuring the acoustic impedance of the ear entails the generation of tones of a specific audio frequency, usually 220 or possibly 660 Hz, fed to the ear canal through a suitable probe. Though the same technique could be applied with other frequencies in the range of interest, the switchover from one frequency to the other and the amplitude measurements needed in each instance would require a lengthy procedure and would thus be inconvenient especially for diagnostic purposes.